The present invention relates generally to belting, and more specifically relates to belting for use in agricultural equipment such as hay balers.
The design and construction of belting for use in agricultural equipment such as hay balers presents considerations not found in other environments. Belts utilized in hay balers for forming round bales ("round hay balers") may be on the order of 40 feet in length. Throughout their length, the belts must be able to support heavy loads with a minimum of stretching and must withstand extreme environmental conditions without deteriorating.
When a belt for a round hay baler is subjected to heavy loading under operating conditions, the amount that the belt stretches must remain within a certain tolerance or the bale being made will become too large, thereby interfering with proper baler operation, and will not be compacted and formed properly.
The amount of stretch which may occur in belts used on hay balers is not insignificant. For example, a typical maximum specification for elongation of belts for hay balers has been three percent at a specified load. A forty foot belt is thus permitted to stretch up to about fourteen inches under that load. When the belt stretches beyond tolerable limits, the belt is removed and shortened. This shortening of the belt has typically been accomplished by trial and error techniques, especially in the field. Such trial and error techniques can produce unsatisfactory results.
Manufacturers of hay balers have continued to increase the specification for the density of bales which a baler can produce. The amount of loading to which the belts of the baler are subjected in the making of denser bales is increased, and hence the likelihood that a belt will stretch by an amount beyond acceptable limits for proper operation is increased.
Another factor to be considered in belt design is the ability of the belt to flex in operation without the ply material cracking. In that regard, a typical round hay baler employs a plurality of rollers on which the belts are installed. The position of the rollers is such that the belts are subjected to a substantial amount of flexing in traveling around the rollers. Moreover, some of the rollers are positioned such that the belts must travel in and S-shape during operation. If the belts fail due to the flexing stress, the belt must be replaced to recover proper operation of the baler.
Belting having the excellent characteristics of being able to flex in the warp direction while at the same time being resistant to stretching is described in U.S. Pat. No. 4,371,580, which is assigned to the assignee of the present application. The specification of U.S. Pat. No. 4,371,580 is incorporated herein by reference. The belting described in the '580 patent includes three plies of synthetic fabric. The fabric used in each of the outer plies has a flex fatigue life and an elongation modulus which are greater than the respective flex fatigue life and elongation modulus of the fabric used in the center ply. The center fabric ply thus limits the amount that the belt can stretch, while the fabrics used in the outer plies provide the belt with excellent flexing characteristics.
The typical mechanism for connecting the ends of the belt to form a continuous loop is with a "clipper splice" (for example, as shown in FIGS. 3a and 3b). The likelihood of belt failure due to flexing is most pronounced in the vicinity of the clipper splice. The belting of the '580 patent is believed to have solved this problem.
However, prior to the present invention, a problem which still existed in belts for hay balers resulted from the contact between the belt and its guides. Each belt is installed on the baler between a pair of guides, and the guides are essential to prevent the belts from moving transversely and becoming entangled with one another. Each belt is permitted to move sideways between its guides, and in doing so and edge of the belt sometimes contacts the guide on its side. When this happens, the edges of prior art belts do not move away from the guide, but instead the edges often end up "riding" on a guide for successive revolutions of the belt. In this situation, one end of the clipper splice may repeatedly be stuck by the guide, eventually causing the splice to break. Also, when the edge of the belt "rides" on the guide, the belt is prone to "cup", and possibly even to flip over. Neither of these conditions constitutes desirable operating conditions.